For many years, double acting piston pumps have been used to pump various types of viscous materials. With higher viscosity materials, so-called shovel pumps or priming piston pumps are well known, one example being manufactured by the Assignee of the instant invention under the trademark Bulldog.RTM. and bearing part number 204-287 (the contents of the attached manual for that product are hereby incorporated by reference.)
While such pumps generally work well with higher viscosity materials, some extremely high viscosity materials are hard to load and do not pump well. The prior art devices have generally utilized a metal shovel plate assembly having a substantial amount of clearance (on the order of 0.2 inch) between the disk and the intake cylinder.